PROJECT SUMMARY Substance use disorder (SUD) is a significant public health challenge that costs the US over $740 billion annually and lacks the current workforce to address it. Our proposed innovation, SUDCare, is a novel and intelligent mobile application that will be designed to address the pressing needs of primary care patients who have inadequate resources and services for SUD screening and follow-up care. The core components of the proposed innovation will consist of a remote screening tool for the assessment of patients? risk level of SUD and a chatbot to support logistical and routine queries. Our research team will utilize natural language processing (NLP) and machine learning techniques to create a scalable and sustainable solution to support an evidence-based SUD screening and treatment protocol. SUDCare has the potential to streamline follow-up clinic encounters and minimize the increasing workload burden placed on PCPs while filling a largely unfilled gap in care for hard-to- reach populations not directly served by any SUD therapeutic solutions available today. The goal of this SBIR Phase I project is to test technical merit, feasibility, and commercial potential of SUDCare. We will accomplish this goal using a user-centered design framework following three specific aims. In Aim 1, we will conduct semi- structured formative interviews with stakeholders (i.e., primary care providers, nurses, care coordinators, insurers, health IT specialists) and potential target end users (i.e., patients) (Substudy 1, N=20) recruited from our partnering primary care clinic. The data collected from this Substudy will be used to support the SUDCare development and requirements for integration with clinic workflow and systems. In Aim 2, we will build a working prototype of SUDCare. To create the chatbot prototype, we will train an English language model using a rich, existing de-identified dataset of text-message conversations from previous related work. Finally, in Aim 3, we will assess the acceptability of SUDCare through usability testing conducted with patients at risk of SUD (Substudy 2, N=8). Results from Phase I will inform a potential Phase II project to further develop SUDCare and conduct a larger-scaled pilot study to evaluate the efficiency and effectiveness of SUDCare.